全文获取类型
收费全文 | 8241篇 |
免费 | 726篇 |
出版年
2024年 | 9篇 |
2023年 | 89篇 |
2022年 | 179篇 |
2021年 | 323篇 |
2020年 | 187篇 |
2019年 | 239篇 |
2018年 | 272篇 |
2017年 | 230篇 |
2016年 | 367篇 |
2015年 | 564篇 |
2014年 | 544篇 |
2013年 | 667篇 |
2012年 | 780篇 |
2011年 | 720篇 |
2010年 | 459篇 |
2009年 | 350篇 |
2008年 | 488篇 |
2007年 | 426篇 |
2006年 | 375篇 |
2005年 | 330篇 |
2004年 | 307篇 |
2003年 | 266篇 |
2002年 | 232篇 |
2001年 | 37篇 |
2000年 | 23篇 |
1999年 | 37篇 |
1998年 | 59篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 25篇 |
1992年 | 9篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有8967条查询结果,搜索用时 15 毫秒
91.
Sara Marin Anaïs Gibert Juliette Archambeau Vincent Bonhomme Mylne Lascoste Benoit Pujol 《Molecular ecology》2020,29(16):3010-3021
Phenotypic divergence among natural populations can be explained by natural selection or by neutral processes such as drift. Many examples in the literature compare putatively neutral (FST) and quantitative genetic (QST) differentiation in multiple populations to assess their evolutionary signature and identify candidate traits involved with local adaptation. Investigating these signatures in closely related or recently diversified species has the potential to shed light on the divergence processes acting at the interspecific level. Here, we conducted this comparison in two subspecies of snapdragon plants (eight populations of Antirrhinum majus pseudomajus and five populations of A. m. striatum) in a common garden experiment. We also tested whether altitude was involved with population phenotypic divergence. Our results identified candidate phenological and morphological traits involved with local adaptation. Most of these traits were identified in one subspecies but not the other. Phenotypic divergence increased with altitude for a few biomass‐related traits, but only in A. m. striatum. These traits therefore potentially reflect A. m. striatum adaptation to altitude. Our findings imply that adaptive processes potentially differ at the scale of A. majus subspecies. 相似文献
92.
Knowledge of zooplankton in situ diet is critical for accurate assessment of marine ecosystem function and structure, but due to methodological constraints, there is still a limited understanding of ecological networks in marine ecosystems. Here, we used DNA‐metabarcoding to study trophic interactions, with the aim to unveil the natural diet of zooplankton species under temporal variation of food resources. Several target consumers, including copepods and cladocerans, were investigated by sequencing 16S rRNA and 18S rRNA genes to identify prokaryote and eukaryote potential prey present in their guts. During the spring phytoplankton bloom, we found a dominance of diatom and dinoflagellate trophic links to copepods. During the summer period, zooplankton including cladocerans showed a more diverse diet dominated by cyanobacteria and heterotrophic prey. Our study suggests that copepods present trophic plasticity, changing their natural diet over seasons, and adapting their feeding strategies to the available prey spectrum, with some species being more selective. We did not find a large overlap of prey consumed by copepods and cladocerans, based on prey diversity found in their guts, suggesting that they occupy different roles in the trophic web. This study represents the first molecular approach to investigate several zooplankton–prey associations under seasonal variation, and highlights how, unlike other techniques, the diversity coverage is high when using DNA, allowing the possibility to detect a wide range of trophic interactions in plankton communities. 相似文献
93.
Christian Kiffner John Kioko Jack Baylis Camille Beckwith Craig Brunner Christine Burns Vasco Chavez‐Molina Sara Cotton Laura Glazik Ellen Loftis Megan Moran Caitlin O'Neill Ole Theisinger Bernard Kissui 《Ecology and evolution》2020,10(18):10000-10016
Facilitating coexistence between people and wildlife is a major conservation challenge in East Africa. Some conservation models aim to balance the needs of people and wildlife, but the effectiveness of these models is rarely assessed. Using a case‐study approach, we assessed the ecological performance of a pastoral area in northern Tanzania (Manyara Ranch) and established a long‐term wildlife population monitoring program (carried out intermittently from 2003 to 2008 and regularly from 2011 to 2019) embedded in a distance sampling framework. By comparing density estimates of the road transect‐based long‐term monitoring to estimates derived from systematically distributed transects, we found that the bias associated with nonrandom placement of transects was nonsignificant. Overall, cattle and sheep and goat reached the greatest densities and several wildlife species occurred at densities similar (zebra, wildebeest, waterbuck, Kirk's dik‐dik) or possibly even greater (giraffe, eland, lesser kudu, Grant's gazelle, Thomson's gazelle) than in adjacent national parks in the same ecosystem. Generalized linear mixed models suggested that most wildlife species (8 out of 14) reached greatest densities during the dry season, that wildlife population densities either remained constant or increased over the 17‐year period, and that herbivorous livestock species remained constant, while domestic dog population decreased over time. Cross‐species correlations did not provide evidence for interference competition between grazing or mixed livestock species and wildlife species but indicate possible negative relationships between domestic dog and warthog populations. Overall, wildlife and livestock populations in Manyara Ranch appear to coexist over the 17‐year span. Most likely, this is facilitated by existing connectivity to adjacent protected areas, effective anti‐poaching efforts, spatio‐temporal grazing restrictions, favorable environmental conditions of the ranch, and spatial heterogeneity of surface water and habitats. This long‐term case study illustrates the potential of rangelands to simultaneously support wildlife conservation and human livelihood goals if livestock grazing is restricted in space, time, and numbers. 相似文献
94.
Yasmin Vázquez-Santos Yuriana Martínez-Orea Javier Álvarez-Sánchez Noé Manuel Montaño Sara Lucía Camargo-Ricalde Silvia Castillo-Argüero 《Phyton》2021,90(2):605-619
The aim of this study was to analyze the performance of Acaena elongata colonized by arbuscular mycorrhizal
fungi (AMF) to different phosphorus (P) concentrations, as a measure of AMF dependency. A. elongata, is a species from soils where P availability is limited, such as temperate forests. Our research questions were: 1) How do
different P concentrations affect the AMF association in Acaena elongata, and 2) How does the AMF association
influence A. elongata’s growth under different P concentrations? A. elongata’s growth, P content in plant tissue,
AMF colonization and dependency were measured under four P concentrations: control (0 g P kg−1
), low
(0.05 g P kg−1
), intermediate (0.2 g P kg−1
) and high (2 g P kg−1
) in different harvests. A complete randomized
block design was applied. A. elongata’s growth was higher under -AMF in intermediate and high P concentrations, and the lowest growth corresponded to +AMF in the low and intermediate P concentration. We observed
a negative effect on the root biomass under +AMF in intermediate P concentration, while the P concentration had
a positive effect on the leaf area ratio. The AMF colonization in A. elongata decreased in the highest P concentration and it was favored under intermediate P concentration; while the low and the high concentrations generated a cost-benefit imbalance. Our results suggest that the performance of some plant species in soils with
low P availability may not be favored by their association with AMF, but a synergy between AMF and intermediate P concentrations might drive A. elongata’s growth. 相似文献
95.
96.
97.
98.
Hansford Kayleigh M. McGinley Liz Wilkinson Samantha Gillingham Emma L. Cull Ben Gandy Sara Carter Daniel P. Vaux Alexander G. C. Richards Simon Hayes Alister Medlock Jolyon M. 《Experimental & applied acarology》2021,84(3):593-606
Experimental and Applied Acarology - Assessing the risk of tick-borne disease in areas with high visitor numbers is important from a public health perspective. Evidence suggests that tick presence,... 相似文献
99.
100.
Ventura Luigi Gnetti Letizia Rossi Maurizio Tiseo Marcello Giordano Giovanna Corradi Massimo Silva Mario Milanese Gianluca Minari Roberta Leonetti Alessandro Cattadori Sara Ampollini Luca Carbognani Paolo Mozzoni Paola 《Molecular biology reports》2021,48(4):3485-3494
Molecular Biology Reports - Benign metastasizing leiomyoma (BML) is a rare disease characterized by extrauterine benign leiomyomatosis in patients with a previous or concomitant history of uterine... 相似文献